Indeed, my tiny pocket knife (a gift from Jeremy—well, he was throwing it away and I salvaged it it—visible at left in this photo), was in my bag, and the TSA agent had spotted its tiny profile on his screen.
It had been living in the bottom of my pencil/pen case for quite some time; it tucks away there perfectly—being smaller than most multitools—and I can’t count the number of times it’s come in handy for:

Gently prying apart seams on electronics (using the large blade)

Extracting stubborn jumpers (w/ tweezers)

Clipping/cutting clothing tags, zip-ties, twist-ties, etc (scissors)

Assorted screw-driving

Other tasks that require both urgency and a small blade: breaking down boxes, opening envelopes, dispatching errant threads

(Apparently, Victorinox could just leave off the nail file.)

I really had forgotten that I’ve been carrying it there—in fact, I hadn’t been able to find it in the last few weeks, so I wasn’t entirely sure where it was. (This prompts me to consider a new use for the TSA screening process: locating lost items. “Uh, mister X-ray technician, can you tell me if my flash drive is in there somewhere?”)

Conclusions:

BWI TSA agents are careful and thorough.

IAH, not so much.

This corroborates the findings of the Atlantic article: preventing contraband from entering an airplane is, at best, probabilistic, like any kind of random audit.

I am not a terrorist—and what’s more, I didn’t even realize I had the knife with me—so I can guarantee that the plane was no safer without my particular contraband than with it.